Could a common bacteria cure cancer?

In its natural form, Clostridium novyi is at best benign (it lives in the soil) and at worst harmful (it can cause infections). But a slightly modified version of the bacterium could be a completely new treatment for cancer. Injecting thousands of spores of a modified C novyi into rats, dogs, and one human patient shrank or even eradicated their tumours.

The intriguing study published this week in Science Translational Medicine describes how to harness the bacteria's natural ability to attack cells for good. C novyi likes oxygen-poor environments - like the soil or, in this case, deep inside dense tumours - where chemotherapy and radiation can't penetrate.

To make it safer as a cancer treatment, the C novyi was modified to take out a gene for toxins. The team, led by researchers at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center, tested C novyi in rats, later 16 dogs and after promising results, tested the treatment in a human patient.

The bacteria make enzymes that broke through cell wells, then gobble up the proteins spilled by the cancerous cells. Now, more human trials are underway. It's just one study so far, but it is promising evidence that bacteria therapy for cancer could work.

The idea has been studied for decades, but other bacteria used to treat cancer were too dangerous and inconsistent in their effectiveness. C novyi seems to be an improvement. Bacteria and viruses that make us sick, after all, are already exquisitely engineered to attack our cells - we just need to prompt them to attack the right ones.